The present invention relates to a fingerprint input apparatus for inputting fingerprints to register them or collate them with fingerprints already registered.
None of the fingerprints of different people coincide with each other, and the fingerprints do not change throughout their lives. Owing to these characteristics of fingerprints, fingerprint collation systems are especially used in the fields that require high degrees of security. An apparatus for inputting fingerprint images is a constituent element of such a fingerprint collation system. This fingerprint input apparatus includes an optical system as a constituent. The collation precision of the fingerprint collation system greatly depends on whether fingerprint images can be correctly input.
Any conventional fingerprint input apparatus, however, cannot obtain high-quality fingerprint images.
The present invention has been made to solve this problem, and has as its object to provide a fingerprint input apparatus which can obtain high-quality fingerprint images.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a fingerprint input apparatus comprising a prism placed such that a surface in one direction serves as a fingerprint collection surface, a light source for irradiating light on the fingerprint collection surface through the prism, a pinhole set in a path of light which is reflected by a pattern surface of a finger placed on the fingerprint collection surface and emerges from the prism, and an imaging place on which the light emerging from the prism and passing through the pinhole is formed into an image, wherein when the prism is substituted by air, an optical fingerprint collection surface equivalent to the fingerprint collection surface is set to be substantially parallel to the imaging plane.
According to this aspect, light reflected by the pattern surface of the finger directly or indirectly placed on the fingerprint collection surface and emerging from the prism passes through the pinhole and is formed into an image on the imaging plane set to be almost parallel to the optical fingerprint collection surface of the prism.
According to the second aspect of the present invention, in the first aspect, when the optical fingerprint collection surface has distortion with respect to the fingerprint collection surface, the imaging plane is rotated through a predetermined angle. According to this aspect, distortion caused on the optical fingerprint collection surface can be reduced by rotating the imaging plane almost parallel to the optical fingerprint collection surface of the prism through a predetermined angle.
According to the third aspect of the present invention, there is provided a fingerprint input apparatus comprising a first prism placed such that a surface in one direction serves as a fingerprint collection surface, a light source for irradiating light on the fingerprint collection surface through the first prism, a pinhole set in a path of light which is reflected by a pattern surface of a finger placed on the fingerprint collection surface and emerges from the first prism, an imaging plane on which the light emerging from the first prism and passing through the pinhole is formed into an image, and a second prism placed in front of the imaging plane, wherein the fingerprint collection surface of the first prism is set to be substantially parallel to the imaging plane, the fingerprint collection surface of the first prism is set to be substantially parallel to a surface of the second prism on the imaging plane side, and an exit surface of the first prism with respect to the pinhole is set to be substantially parallel to an incident surface of the second prism with respect to the pinhole.
According to this aspect, the optical system on the first prism side is made similar to the optical system on the second prism side with the pinhole being the center, and light reflected by the pattern surface of the finger directly or indirectly placed on the fingerprint collection surface and emerging from the first prism passes through the pinhole and the second prism and is formed into an image on the imaging plane.
According to the fourth aspect of the present invention, in the first, second, and third aspects, the apparatus further comprises pinhole position adjusting means for adjusting a position of the pinhole. According to this aspect, the position and size of a fingerprint image on the imaging plane can be changed by adjusting the position of the pinhole in the back-and-forth direction, the lateral direction, the vertical direction, and the like.
According to the fifth aspect of the present invention, in the fourth aspect, the pinhole position adjusting means is constituted by a manual adjusting mechanism, and the apparatus further comprises a display section for displaying a fingerprint image formed on the imaging plane. According to this aspect, the user can change the position and size of a fingerprint image on the imaging plane by adjusting the position-of the pinhole in the back-and-forth direction, the lateral direction, the vertical direction, and the like while seeing the displayed fingerprint image.
According to the sixth aspect of the present invention, the pinhole position adjusting means automatically adjusts the position of the pinhole. According to this aspect, the position of the pinhole is automatically adjusted, and the position and size of a fingerprint image on the imaging plane are adjusted to set values.
According to the seventh aspect of the present invention, in the first, second, and third aspect, the light source is an LED or a laser beam radiator. According to this aspect, light from an LED or a laser beam radiator, i.e., light having a single wavelength, is irradiated on the fingerprint collection surface through the prism.
According to the eighth aspect of the present invention, there is provided a fingerprint input apparatus comprising a prism placed such that a surface in one direction serves as a fingerprint collection surface, a light source for irradiating light on the fingerprint collection surface through the prism, a pinhole set in a path of light which is reflected by a pattern surface of a finger placed on the fingerprint collection surface and emerges from the prism, a lens placed close to a rear side of the pinhole, and an imaging plane on which the light emerging from the prism and passing through the pinhole and the lens is formed into an image, wherein when a straight line connecting a center of the fingerprint collection surface and a center of the imaging plane is an optical axis, the imaging plane is inclined with respect to the optical axis to prevent blur, and a central axis of the lens is inclined with respect to the optical axis to prevent trapezoidal distortion.
According to this aspect, the light intensity of a fingerprint image formed on the imaging plane is increased by the lens placed close to the rear side of the pinhole. In this case, a blur is suppressed by inclining the imaging plane with respect to the optical axis, and trapezoidal distortion is suppressed by inclining the central axis of the lens with respect to the optical axis under the condition in which this blur is suppressed.
According to the ninth aspect of the present invention, in a fingerprint input apparatus based on the optical path separation method, a cut surface is formed at a distance from a vertex of the prism which opposes the fingerprint collection surface, and the light source is placed to oppose the cut surface of the prism. According to this aspect, light from the light source is incident on the prism through the cut surface to be irradiated on the fingerprint collection surface with an almost uniform diffusion angle.
According to the 10th aspect of the present invention, in the ninth aspect, the cut surface is formed under conditions that an imaging optical path of light from the fingerprint collection surface to the imaging plane is not shielded, and an image of the light source is not projected on the imaging plane. According to this aspect, the imaging optical path of light from the fingerprint collection surface to the imaging plane is not shielded in the prism, and an image of the light source is not projected on the imaging plane.
According to the 11th aspect of the present invention, in the ninth aspect, the cut surface is formed under conditions that an imaging optical path of light from the fingerprint collection surface to the imaging plane is not shielded, an image of the light source is not projected on the imaging plane, and light from the light source is not totally reflected by the fingerprint collection surface. According to this aspect, the imaging optical path of light from the fingerprint collection surface to, the imaging plane is not shielded in the prism, and an image of the light source is not projected on the imaging plane. In addition, light from the light source is not totally reflected by the fingerprint collection surface.
According to the 12th aspect of the present invention, in the ninth aspect, the cut surface is formed under a condition that an imaging optical path of light from the fingerprint collection surface to the imaging plane is not shielded, and a light shield is provided for a region, on the cut surface, on which an image of the light source can be projected. According to this aspect, the imaging optical path of light from the fingerprint collection surface to the imaging plane is not shielded in the prism. In addition, since the light shield is provided for the cut surface, there is no possibility that an image of the light source is projected on the imaging plane.
According to the 13th aspect of the present invention, in the ninth to 12th aspects, the cut surface of the prism is a concave surface. According to this aspect, light from the light source is incident on the prism through the concave cut surface and irradiated on the fingerprint collection surface with a uniform diffusion angle.
According to the 14th aspect of the present invention, in the 13th aspect, the cut surface of the prism has a convex outer periphery. According to this aspect, light from the light source is diffused by the concave inner surface of the cut surface, and is focused by the convex surface of the outer periphery of the cut surface to be irradiated on the fingerprint collection surface.
According to the 15th aspect of the present invention, in a fingerprint input apparatus based on the optical path separation method, the light source is placed in contact with the prism through a matching member having a predetermined refractive index. According to this aspect, light from the light source is incident on the prism through the matching member to be irradiated on the fingerprint collection surface with a almost uniform diffusion angle.
According to the 16th aspect of the present invention, there is provided a fingerprint input apparatus comprising a prism placed such that a surface in one direction serves as a fingerprint collection surface, and a light source mounted on a surface of a substrate and serving to irradiate light on the fingerprint collection surface through the prism, wherein a film having a high reflectance is formed on the surface of the substrate on which the light source is mounted. According to this aspect, light leaking from the side and rear surfaces of the light source is reflected by the reflecting film on the substrate surface and incident on the prism.
According to the 17th aspect of the present invention, there is provided a fingerprint input apparatus comprising a prism placed such that a surface in one direction serves as a fingerprint collection surface, and a light source mounted on a surface of a substrate and serving to irradiate light on the fingerprint collection surface through the prism, wherein a film-for shielding light is formed on the surface of the substrate on which the light source is mounted. According to this aspect, light leaking from the side and rear surfaces of the light source is shielded by the light-shielding film on the substrate surface, thereby preventing the light from passing through the substrate and leaking out from its rear surface.
According to the 18th aspect of the present invention, there is provided a fingerprint input apparatus comprising a prism placed such that a surface in one direction serves as a fingerprint collection surface, and a light source mounted on a surface of a substrate and serving to irradiate light on the fingerprint collection surface through the prism, wherein a film (reflecting/light-shielding film) having a high reflectance and shielding light is formed on the surface of the substrate on which the light source is mounted. According to this aspect, light leaking from the side and rear surfaces of the light source is reflected by the reflecting/light-shielding film on the substrate surface and incident on the prism. In addition, light leaking from the side and rear surfaces of the light source is shielded by the reflecting/light-shielding film on the substrate surface, thereby preventing the light from passing through the substrate and leaking from its rear surface.
According to the 19th aspect of the present invention, there is provided a fingerprint input apparatus comprising a prism placed such that a surface in one direction serves as a fingerprint collection surface, and a light source for irradiating light on the fingerprint collection surface through the prism, an imaging plane on which light reflected by a pattern surface of a finger placed on the fingerprint collection surface and emerging from the prism is formed in to an image, a prism holder for holding the prism to fix the fingerprint collection surface such that the fingerprint collection surface opposes a finger mount portion opening of a main body case, the prism holder having an opening at least in a surface portion opposing an exit surface of the prism and an incident surface of the prism on which light from the light source is incident, and a light-shielding cover for covering an imaging optical path between the exit surface of the prism and the imaging plane while isolating the optical path from the outside.
According to the 20th aspect of the present invention, in the 19th aspect, an optical noise process is performed for a surface of an inner wall of the light-shielding cover.
According to the 21st aspect of the present invention, in the 19th or 20th aspect, a film having a high reflectance is formed on a surface of an outer all of the light-shielding cover.
According to the 22nd aspect of the present invention, in the 19th aspect, the light source is covered with a light source cover except for a portion on the exit surface side with respect to the prism, and the light source cover and the light-shielding cover are integrally formed.
According to the 23rd aspect of the present invention, in the 22nd aspect, a film having a high reflectance is formed on a surface of an inner wall of the light source cover.
According to the 24th aspect of the present invention, there is provided a fingerprint input apparatus comprising a prism placed such that a surface in one direction serves as a fingerprint collection surface, a light source for irradiating light on the fingerprint collection surface through a prism, an imaging plane on which light reflected by a pattern surface of a finger placed on the fingerprint collection surface and emerging from the prism is formed into an image, a prism holder for holding the prism to fix the fingerprint collection surface such that the fingerprint collection surface opposes a finger mount portion opening of a main body case, the prism holder having openings at least in a surface portion opposing an exit surface of the prism and an incident surface of the prism on which light from the light source is incident, an imaging plane case for storing the imaging plane, the case having an opening on the exit surface side of the prism. and a light-shielding cover for covering an imaging optical path between the exit surface of the prism and the imaging plane while isolating the optical path from the outside, wherein an opening of the light-shielding cover on one end side is coupled to the opening of the prism holder which opposes the exit surface of the prism with a fitting structure, and an opening of the light-shielding cover on the other end side is coupled to the opening of the imaging plane case with a fitting structure.